1. Field of the Invention
The present invention relates to an apparatus and method to control the focusing of a photographing device, and more particularly, to an apparatus and method to control the focusing of a photographing device, the apparatus and method capable of removing a light source portion from an image and controlling the focusing of the photographing device according to whether the image is in a high-illuminance state or a low-illuminance state.
2. Description of the Related Art
Generally, photographing devices, such as camcorders and cameras, photoelectrically convert optical signals incident through a lens into electrical signals and perform a predetermined image processing operation on the photoelectrically converted image signals. In this way, the photographing devices perform a photographing operation. Photographing devices perform a focusing operation using an automatic focusing method or a manual focusing method.
In the automatic focusing method, the position of a lens is automatically adjusted to a position having maximum auto focus data in an area between a subject and the lens located a predetermined distance away from the subject. The auto focus data denotes a contrast value according to a luminance value in the area between the subject and the lens. When the automatic focusing method is used, the position of the lens is automatically adjusted to a position that provides the clearest image without user manipulation.
In addition, while photographing a main subject in a stable manner, if a photographing device senses a large change in the auto focus data, the lens of the photographing device focuses on a new subject.
In a backlight state, if the lens is out of focus, the outline of a light source becomes large due to blurring. In this case, if the automatic focusing method in which the lens is focused based on luminance is used, the outline of the light source becomes large even when the lens is out of focus, and thus the auto focus data becomes maximized.
Furthermore, in a low illuminance state, there is little difference in contrast according to luminance between when the lens is in focus and when the lens is out of focus. Therefore, it is difficult to precisely focus the lens.
Japanese Patent Publication No. 1995-030798 discloses a conventional auto focus camera detecting a high-luminance component, controlling a reference level of a high pass filter (HPF) by adjusting an amplification factor of an image signal, and calculating a focusing estimate by removing a low-level signal from an output of the HPF. However, the conventional auto focus camera sets the reference level of the HPF according to the amplification factor by which an average level of an image is amplified. Therefore, if a light source portion exists in the image, an edge component becomes large when the lens is out of focus. Accordingly, an output value of the HPF becomes large.